1. Field of the Invention
The present invention relates to a storage device such as a disk drive, an error recovery processing method for execution therein.
2. Description of Related Art
A disk drive device using a magnetic disk as a recording medium uses a head for recording and reproducing data on the magnetic disk. This head is installed under the bottom surface (nearest the surface of the magnetic disk) of a head/slider having an air bearing surface. The terms xe2x80x9cheadxe2x80x9d and xe2x80x9csliderxe2x80x9d are used somewhat interchangeably in the art unless it is clear from the context that another meaning is implied. The slider is installed at an end of an arm, which moves the slider in an arcuate, nearly radial direction over the magnetic disk by a rotary actuator or voice coil motor (VCM).
In addition, the slider is urged toward the magnetic disk by an elastic suspension member installed in the arm. When air flows into between the head slider and magnetic disk with the rotation of the magnetic disk, the slider floats or flies up from the magnetic disk surface against resistance of the elastic member. A gap between the magnetic disk and slider is a predetermined value determined in part by the relative speed between the air bearing surface of the slider and magnetic disk.
The gap between the slider and magnetic disk may become too small if the slider is deformed by thermal expansion or the like and a specific portion protrudes toward the magnetic disk. In addition, the surface of the magnetic disk inevitably has a certain degree of asperity. The slider may even collide with an asperity on the surface of the magnetic disk. If a collision occurs, local temperatures in the slider may sharply increase due to frictional heat and the like. The term xe2x80x9cthermal asperityxe2x80x9d is used for this condition.
In particular, a magnetic transducer (or head) using an MR (magnetoresistance effect) element or a GMR (giant magnetoresistance effect) element suffers decreased reliability since an increase of the temperature leads to a large change of the output signal. In some cases, the head will not function at all.
For this reason, conventionally, there are disk drive devices with countermeasures such as correction of a head output caused by the temperature change with using a DC component of the reproduced output of the head. Nevertheless, there are many cases where it is not sufficient to only correct the head output at the time of the thermal asperity.
In addition, there can be areas where the thermal asperity occurs permanently. Therefore, for example, as disclosed in Published Unexamined Patent Application No. 9-251727, there are disk drive devices where each area where the thermal asperity occurs permanently is marked as a defective sector.
Since positional information is conventionally is detected on the basis of signals output by the head which are generated by from servo sector information recorded on the disk, thermal asperities may result in the servo sector information being missed.
For this reason, a method is devised to estimate a slider""s position with using appropriate positional information such as a reproduced output from a previous servo sector even if a servo sector just before a data sector is not correctly reproduced.
It may be possible to read and write in an area, which has been designated as an area where the thermal asperity has occurred permanently, so long as head temperature falls thereafter. In these cases the number of defective sectors increases unnecessarily.
The present invention is made in consideration of the above problems and provides a disk drive device and an error recovery processing method for execution therein which contribute to maintenance of recording capacity and to enhancement of reliability by recovering from errors caused by temporary conditions which prior art drives treat as permanent errors.
A disk drive device according to the present invention comprises means for detecting an error occurring during reading or writing, means for executing a first error recovery procedure on the failing location, means for executing a second error recovery procedure on the failing location only after predetermined waiting time elapses.
In addition, a disk drive embodiment according to the invention can include a temperature sensor for detecting a temperature at the disk drive (either inside or outside the disk drive, and an error processing means which sets the waiting time between the first and second error recovery procedures according to the temperature detected to allow time for the temperature to decline and thereby increasing the likelihood of recovery.
Furthermore, another disk drive embodiment according to the invention includes alternative area (typically a sector) assigning means for taking a failing area out of service by performing temporarily assigning (registering) an alternative area to serve in the place of the failing area. The temporary registration is subsequently retested or confirmed after a time period has elapsed by executing a second error recovery procedure. The temporary registration is cancelled if the previously failing area now passes, i.e., the area is recovered. The temporary registration may be made permanent, i.e., changed to a regular registration if the area is not recovered.